How to create random function using a stored procedure? PL/SQL - sql

Question

I have a procedure that adds data
add_price (cust_id customers.id%type,
items_id items.id%type,
price number);
and I want to create a function that for each combination of customers and items to create an additional one at random entry in the table price.
How can I do that?

Answer 1

UPD: Please note, I believe the idea from MT0 is better because you'll need only one insert statement. My solution is for the case when using add_price function is required
So, "each combination of customers and items" means you need a cartesian product:
select cust_id, item_id
from customers
cross join items;
For example if you had following data in "customers" and "items" table:
cust_id
cust_name
1
A
2
B
item_id
item_name
1
a
2
b
the query above would return:
cust_id
item_id
1
1
1
2
2
1
2
2
Thus, all is left is to get random value. Use dbms_random.value for that
begin
for q in (select cust_id, item_id from customers cross join items) loop
add_price(q.cust_id, q.item_id, round(dbms_random.value(10, 1000), 2));
end loop;
end;
The parameters for value are lowes_value and highest_value so the result will be between those numbers. You probably will need to set them somehow. And rounding will be needed too

Answer 2

Don't use a function, create a procedure and use INSERT ... SELECT with the CROSS JOIN of the customers and the items tables:
CREATE PROCEDURE generate_random_prices
IS
BEGIN
INSERT INTO prices (customer_id, item_id, price)
SELECT c.customer_id,
i.item_id,
ROUND(DBMS_RANDOM.VALUE(0,100),2)
FROM customers c
CROSS JOIN items i;
END generate_random_prices;
/
Which, if you have the sample data:
CREATE TABLE customers (customer_id PRIMARY KEY) AS
SELECT COLUMN_VALUE FROM TABLE(SYS.ODCINUMBERLIST(1,5,42));
CREATE TABLE items (item_id PRIMARY KEY) AS
SELECT COLUMN_VALUE FROM TABLE(SYS.ODCINUMBERLIST(1,3,61));
CREATE TABLE prices (
customer_id REFERENCES customers(customer_id),
item_id REFERENCES items(item_id),
price NUMBER(4,2)
);
Then after:
BEGIN
generate_random_prices();
END;
/
The prices table may (randomly) contain:
CUSTOMER_ID
ITEM_ID
PRICE
1
1
38.91
1
3
39.74
1
61
67.28
5
1
13.92
5
3
48.17
5
61
70.21
42
1
90.33
42
3
5.7
42
61
40.37
If you want to call your ADD_PRICE procedure then just take the same CROSS JOIN query and use a cursor loop:
CREATE PROCEDURE generate_random_prices
IS
BEGIN
FOR rw IN (SELECT c.customer_id,
i.item_id
FROM customers c
CROSS JOIN items i)
LOOP
ADD_PRICE(rw.customer_id, rw.item_id, ROUND(DBMS_RANDOM.VALUE(0,100),2));
END LOOP;
END generate_random_prices;
/
(But it will be more efficient to just use a single INSERT ... SELECT statement.)
db<.fiddle here